Abstract

We use roll-call voting data from 16 legislatures to investigate how the institutional context of politics – such as whether a country is a parliamentary or presidential regime, or has a single-party, coalition or minority government – shapes coalition formation and voting behaviour in parliaments. We use a geometric scaling metric to estimate the ‘revealed space’ in each of these legislatures and a vote-by-vote statistical analysis to identify how much of this space can be explained by government-opposition dynamics as opposed to (leftright) policy positions of parties. We find that government-opposition interests rather than parties’ policy positions are the main drivers of voting behaviour in most institutional contexts. In contrast, we find that issue-by-issue coalition-building along a single policy dimension only exists under restrictive institutional constraints; namely presidential regimes with coalition governments or parliamentary systems with minority governments. Put another way, voting in most legislatives is more like Westminster than Washington, DC.